Will Gray

Tech Talk: What are F1’s infrared secrets?

Will Gray

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The new infrared cameras introduced at recent Grands Prix have proved an instant hit with F1 fans – but how do they work and what exactly do they show?

Teams have been allowed to use their own cameras in Friday practice sessions for some time, but last year Red Bull was the first on record to add infrared on-boards to their armoury of analysis tools.

They placed a thermographic camera on their engine cover, pointed at the Coanda exhaust exits, with the likely focus on analysing how the hot gas flow and cold air interacted on its way to the all-important diffuser area of the car. The infrared output would effectively give them a real-life version of the virtual CFD visualisation.

Pirelli engineers have also used up to seven infrared cameras during their private track testing and have been able to use the output to perform extremely complex data collection and analysis.

But the new television-friendly version, which first appeared on Paul di Resta’s Force India during the Italian Grand Prix, is a little different.

"The clever bit is actually the transformation of the readings into usable data,” explained Pirelli boss Paul Hembrey. “I was asked what the colours represent; I don't know because I haven't been involved in the calibration."

And that is why this footage works so well for F1 – because although it appears so technical it could offer rival teams extremely useful information, it actually reveals very little detail at all.

So how does it all work?

Visible light is just one small part of the electromagnetic radiation spectrum, a scale that ranges from gamma rays at one end to radio waves at the other. This also includes infrared radiation, which has wavelengths longer than visible light but shorter than radio waves.

Every object emits infrared radiation, but the intensity of what is emitted is a factor of temperature as well as its ability to radiate - known as emissivity.

Anything below 500 degrees Celsius is impossible to detect by human eye – we can feel it, but we just can’t see it – but infrared cameras are used to convert these lower temperatures into visual patterns on a screen.

The cameras consist of an infrared detector made of tiny elements that sit within an electrical circuit. When they absorb incoming thermal radiation, their resistance changes and that effect is converted into a visual image on the screen - initially in grayscale but then usually turned into a scale of colours.

That means nothing, however, until the output is calibrated to convert that to temperature, and that requires knowledge of the radioactive properties of the object – in this case the materials that make up Pirelli’s tyres.

In theory, the different tyre compounds will have different emissivity so working out precise tyre temperatures from these generic FOM clips is virtually impossible.

Also, the sensors used in F1 are the smaller and cheaper un-cooled detectors rather than the expensive and bulky but more accurate cooled versions, so their sensitivity is not good enough, and their reaction time not quick enough, to deliver high levels of accuracy.

But although not highly technical, this footage from Di Resta’s car still gave some interesting background insight into how the tyres are working and how the engineers develop the car to make the most of them.

The footage confirms that the front tyre sidewalls remain very cool at all times, because they are the least loaded part of the car. In cornering, meanwhile, it shows the tyre being loaded up on the outer edge as the colour of the infrared output changes – but what is also clear is that the teams use negative camber to cancel out some of that loading and even out the heating across the tread of the tyre.

In theory, a tyre with an even spread of colour across the tread during cornering is delivering the highest amount of grip with the least amount of temperature degradation.

After the initial experiment at Monza, Felipe Massa carried a rearward-facing camera and that gave the opportunity to see how the rear tyres are affected by temperature during a lap.

Here, the sidewall heats up a lot as the hot air from the exhausts is fed down the gap between them and the diffuser. Under acceleration, the tyres heat up as the power is put through them, and as the speed increases the heat further increases, due to the additional downforce putting more downwards load on the tyres.

The genius of the infrared camera is that it gives fans this level of interesting insight without revealing too much information for the teams. The question is, what can they come up with next? We can only hope the innovation continues...

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